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On the Lookout for FIV

Owners are urged to have their cats tested for feline immunodeficiency virus.

Is your cat a hot-tempered, unneutered male who spends a lot of time
outdoors and seems to like nothing more than scrapping with the other
guys in the neighborhood? If so, he's at especially high risk for
infection with the feline immunodeficiency virus (FIV), a
submicroscopic, parasitic organism that can weaken his immune system
and, in time, make him vulnerable to a host of opportunistic diseases.

Deep bite wounds, notes Julie Levy, DVM, PhD, are, by far, the primary
mode of the virus's transmission from an infected to an uninfected
animal. And pugnacious free-roaming males are more likely, by far, than
other felines to bite them.

Destructive Organisms

Virologists classify FIV as a lentivirus, a slow-acting organism that is
in the same viral family as the potentially deadly human
immunodeficiency virus (HIV), says Dr. Levy, associate professor of
small animal internal medicine at the University of Florida's College of
Veterinary Medicine. But these viruses are species-specific. A cat
cannot contract HIV from a human, and a human cannot be infected by FIV
through contact with an infected cat.

The organism is also classified as a retrovirus, a type of virus
containing reverse transcriptase, an enzyme that converts the viral
genetic material - in this case, RNA or ribonucleic acid - into DNA or
deoxyribonucleic acid that is subsequently inserted into the infected
cat's genetic blueprint. According to Dr. Levy, virus is found in all
body fluids of an infected cat, and is especially abundant in its
saliva.

Following initial infection, virus is carried to the animal's major
lymph nodes, where the organism replicates within disease-fighting white
blood cells called T-lymphocytes. Particularly vulnerable are
lymphocytes known as CD4 cells (or T-helper lymphocytes), which play a
key role in the animal's immune system. This insidious cycle continues
unhampered as the virus circulates throughout the body, invades
additional lymph nodes and destroys more CD4 cells.

Disease Progression

According to Dr. Levy, the earliest stage of infection is likely to pass
unnoticed by the cat's owner. "The animal may run a fever," she says,
"as its white blood cell count decreases. The lymph nodes will swell,
but this is a subtle occurrence and you're probably not going to be
aware of it." In fact, an FIV-positive cat is likely to appear normal
for many years following initial infection.

Eventually, however, evidence of the animal's compromised immune system
will start emerging as the same bacteria, viruses and fungi that
previously existed harmlessly in the animal's normal environment begin
to cause illness.

The most commonly observed clinical signs of FIV infection, says Dr.
Levy, include inflammation of the mucous tissue of the mouth
(stomatitis), inflammation of the middle layer of the eye (uveitis), and
various cancers, especially of the lymphatic tissue (lymphoma).

Some infected cats experience recurrent illness interspersed with
periods of relative good health. In most cats, however, susceptibility
to opportunistic diseases increases progressively as the animal's immune
system is repeatedly challenged by successive episode of illness.

Most Susceptible

Compared to all other feline health threats, FIV infection is "quite
common," according to Dr. Levy. "We estimate that about four percent of
all feral cats in the U.S. are infected," she says. "Looking at all
cats, feral and otherwise, who are diagnosed with FIV, we find that
about 25 percent are female and about 75 percent are male. The condition
is rare among kittens, because they don't start in with their high-risk
behavior until they're older. So, although older cats are more
vulnerable, age in itself is not a determining factor. It's a behavioral
issue."

Although sexual contact is a common mode of transmission in HIV, the
same does not hold true for FIV, says Dr. Levy, despite the virus's
presence in feline semen and other genital secretions. "We don't know
why this is," she says, "but it appears that a cat's immune system is
better able to ward off the virus when it is sexually transmitted than
when it is transmitted by biting."

Likewise, while it is known that HIV can be transmitted from an infected
human mother to her offspring while nursing, this is uncommon in cats. A
queen's milk contains antibodies to FIV-protein substances that the
body produces to weaken or destroy the virus.

These antibodies, Dr. Levy explains, are passed along to a kitten during
its first nursing and "win the battle over the virus most of the time,"
as long as the kitten begins to nurse immediately following its birth,
which most kittens do. (This is not the case in humans.)
"Unfortunately," she points out, "kittens can't absorb the antibodies
after the first day, so if they delay nursing for a day, they are likely
to become infected."

Dr. Levy finds little evidence to support the notion that FIV can be
transmitted by fleas and other such blood-sucking parasites. Similarly,
she disputes the idea that some feline breeds are more susceptible than
others. At the same time, she notes that purebred cats are less
vulnerable due to the "low-exposure" conditions of their environment,
the control of their behavior, and the tendency among breeders to adopt
rigorous FIV testing procedures for their valuable animals.

"There is some evidence that casual contact among friendly animals in a
multiple-cat household increases the risk for infection," says Dr. Levy.
"So they may not be completely safe just because they don't fight."

But the bottom line, she says, is that the vast majority of FIV
infections occur among "outdoor, unneutered male cats that fight and
bite."

Detecting FIV

Diagnosis of infection is based on a cat's history, clinical signs, and
the results of a blood test for FIV antibodies. "All cats should be
tested at least once in their lives," says Dr. Levy. "For a cat who is
not in a high-risk category, the test should be done when you first
acquire the animal. Cats in a high-risk group or those in a multiple-cat
household in which there is an FIV-positive cat or a cat with unknown
FIV status should be tested every year. And just to be safe, a cat who
has recently become ill should be retested."

The presence of antibodies - a "positive" result - indicates that a cat
is infected with FIV and is thus capable of transmitting the virus to
other cats. A "negative" result indicates that antibodies directed
against FIV have not been detected, which usually means that the cat is
not infected. Sometimes, however, the antibody tests are either
inconclusive or conflicting. Depending on a variety of factors, either a
different type of blood test should be done or the cat should be
retested within the following two or three months.

The cost of a blood test for FIV is variable but always relatively
inexpensive, says Dr. Levy, ranging typically from $15 or so in
high-volume veterinary hospitals to about $60 in some private clinics.
Despite the modest outlay, she laments, owners are not doing a good job
of having their animals tested for FIV. "Based on the sales of
blood-sampling kits to veterinarians," she says, "we know that less than
10 percent of cats in the U.S. are tested."

An Optimistic Outlook

Although a vaccine against FIV has been developed, cats that have been
vaccinated will test positive, and its efficacy against all strains of
the virus is yet to be determined. And there is, at present, no remedy
for the infection. But, as Dr. Levy points out, the reasons for testing
for FIV are compelling. One reason, of course, is that testing
identifies those cats that must be kept isolated from others in order to
curb the spread of the infection. As important, she notes, is that
testing identifies cats that will need special attention for the rest of
their lives. Dr. Levy urges owners of FIV-positive cats to approach
their care-giving with optimism.

"Don't treat the test results," she advises. "Instead, treat the cat
that is in front of you. In my experience, FIV-positive cats will
respond very well to treatment if they are diagnosed early and the
problems they encounter are addressed promptly. They can have many years
of high-quality life."